Tilted lens imager in a laser amplifier/oscillator and method utilizing same

Abstract

Lenses (30', 32') are orthogonally tilted with respect to one another in a telescope to provide imaging for an amplifier-phase conjugate mirror (PCM)(10) in a laser oscillator/amplifier (12). This mutually orthogonal tilting avoids the problem of air breakdown which occurs when the laser energy is otherwise focused at a single point and thus avoids the need to use a vacuum cell to suppress the sparking at the telescope's focus. An adjustment of the tilting of one lens (32') with respect to the other lens (30') also avoids astigmatism.

What is claimed is: 
     
       1. Apparatus for imaging an optical path disposed along an axis in a laser oscillator/amplifier comprising: means for generating and directing a beam of laser energy along the optical path; and   first and second lenses for maintaining collimation of the beam along the path, said first and second lenses having an intermediate focal point at which air breakdown occurs,   said lenses being respectively rotated at angles oriented with respect to a normal to the axis of the optical path and orthogonally with respect to one another,   said first lens being rotated a first angle to suppress the air breakdown, said first angle producing astigmatism in the apparatus.   
     
     
       2. Apparatus according to claim 1 further for imaging an optical path in an amplifier-phase conjugate mirror wherein the angle of said second lens is adjusted with respect to that of said first lens for adjusting astigmatism from the apparatus. 
     
     
       3. A method for imaging an optical path disposed along an axis in a laser oscillator/amplifier comprising the steps of: generating and directing a beam of laser energy along the optical path;   maintaining collimation of the beam along the path; and   focussing the beam through sites on the optical path which encompass areas which are greater than a single point,   wherein said focussing step comprises the step of utilizing first and second lenses respectively rotated at angles oriented with respect to a normal to the axis of the optical path and orthogonally with respect to one another, said first and second lenses having an intermediate focal point at which air breakdown occurs, and   rotating said first lens at a first angle to suppress the air breakdown, said first angle producing astigmatism in the optical path.   
     
     
       4. A method according to claim 3 further for imaging an optical path in an amplifier-phase conjugate mirror further comprising the step of adjusting the rotation of the second lens with respect to the first lens for eliminating astigmatism in the optical path. 
     
     
       5. A method according to claim 4 in which said adjusting step comprises the steps of temporarily moving the first lens from its position in the optical path, and tilting the second lens to provide sparking at the phase conjugate mirror focus.